Magnetostrictive transducer lamination



Fil ed Dec. 10, 1952 INVENTOR. Jo/m 17. Will L 0c:

aluml 3 4mm ll/s- 1 77702111675 ..z,ss3,692 FMA'GNETGSTRICTIVE'TRKNSDUGER LAMnsA'rroN Application Deceniber-ltl,152,SerialNo.325,241

6 Claims. 1((21. site-f Giants untier'riuessims coae' 19s2 ,isec.*z66

The invention described therein vmay .beumanufactured and .used.by-.or fortthe.Governmentof the .United States .of. America.for.governmentahpurposes without .the pay- .ment of..any. royalties thereon or therfor. Y

",The ,present. invention relates -to the fabrication .of an electr.oac oustic'.transducer .and :rnore particularly .to ta .magnetostrictive transducer lamination,.the configuration ;of which is-shaped. like.a wagon -wheel.

' Useof the magnetostrictionphenomen'on -atrhigh .fre-

quencies has been restricted due to .the .limitations of physical size of the transducer elements. Tubes and plates and :simple iring :transducers fthat :are r'resonant at frequencies .over -l00.kilocycles .havebeen used but with little success.

The main disadvantage -of the "above-mentioned magnet ostr'icti-ve" elements -is the "sm-allkphysical .size ofthe zresonants'systems in such-transducers. Small resonant systems greatly rreduce ithe input {power and absolute sensitivity permissible. A cylindrical .magnetostrictive "transducer element consisting of ring 'laminations or a scroll Winding of tape capable of resonating at 120 kilocycles or more-has a diameter slightly less than 0.5 inch. As a result of this size the wall thickness of the magnetostrictive structure is very small and the impressed magnetizing force or signal exceeds, at a low power level, the critical limit set by linearity and efficiency. Conversely, such a small element intercepts so little energy in the sound wave that there is a small quantity of energy available after conversion from sound to electrical energy. An array of small transducer elements can be designed but the mounting problem becomes difficult since mounting structures tend to absorb a major portion of the transmitted or received energy.

In contrast to the cylindrical element, the transducer element hereinafter described resembles two concentric cylinders connected by radial spokes having a diameter of approximately 2.6 inches yet having a high resonant frequency, namely 130 kilocycles. An element is composed of a plurality of wagon-wheel shaped laminations providing a resonant element having a high natural frequency that is physically large for frequencies of small wave lengths.

One object of the present invention is to improve the operating characteristics and fabrication of electroacoustic transducers.

Another object of the present invention is to provide an electroacoustic transducer that is physically large but capable of resonating at frequencies of small wave lengths.

Still another object of the invention is to provide a transducer that produces high-frequency acoustic waves with a uniform response pattern in one plane.

A'still further object of the invention is to provide a transducer that produces an uninterrupted alternating 'flux path.

These and other objects of the invention and the vari- Qus features and details of construction and operation .thereof .are hereinafter -more Lfully set forth land de- .scribed .with reference .to .the accompanying drawingsdn .whichQ-likemumbers refer to. like ;parts.

".Eig. .1 is a viewof a wagon-wheel-type laminationiof the invention.

Fig. 2 is a perspective view of a stackwf laminations of. Fig. .1 iformingaamagnetostrictive element.

IFig. 3fis a .sketch.representing.the principleainvolved 'in atwo-mass, one springxsystem.

.The general. shape of the Jami-nation .11 having twelve equallyspacedslots or windows 13 .as --shownin Fig. i1 resembles a wagon wheel. :It can begpunchedlfromany magnetostrictive material .such as "2V Permendur, thy means of a .suitable machine. .Intone construction, tthe laminations '11 are punched .from clean cstri'p stock '.of

0'l'00" 6l-inch'.thick, ihalfhardlv iPermendur approxi- 'matly -217'5 inches wide. The characteristic frequency of half-hard 2V fRermendur of .O.006Finch thicknessis about 'k'ilocycles.v fSai dllaminations .are then cleaned 'and heat-treated "for .one hourin a .dryhydrogen atmosphere 'o'ffSO'O degrees centigrade. -A=coatin-g.-.o-f C-ycle- 'weld' "C -3 is sprayed onlbothsides-of theulaminations to provide 'intei laminationl insulation.

' To fabricate'amagnetostrictive.element or core 17, the laminations are-stacked into-a,packet'one:'inch:in height '(see Fig.2). 'Wi'th/the-aidofiassuitablejigand Cyclerwldi plasticized .cementsaidlaminations .canbe consoliiiattedQ Pressure-release material 23 such as corpreneyis cemented to the inside -ring surface 21-and around the can "be Ziesignedlo-house .s-aid elementel 7.

The 12V ""Pernienilurl.lamination-s are operated atirem- "a'n'ence after'being annealed to-a magnetically half-hard lejgsor 'spokes15. L'Siiitah1e.mounting.means=.rrot.shown) state. (Greater sensitivity can be obtained by using D.-C.

polarized soft nickel.) Coils 19 are wound on alternate legs '15 of the core 17 and are connected in series in such polarity that theflux contributions from adjacent legs add in the bare legs. Thus, each leg is effectively polarized to the same degree when leakage is disregarded.

In the operation of the device, the laminations can be visualized to be composed of a group of resonant systems as shown in Fig. 3. A single spoke 15 with its inner and outer mass can most readily be compared to a two-ma'ss, one-spring system with a node 31 at the middle of the spring 39. A radiating face or surface 33 on mass 35 operates into a medium or load 37. The size of mass 35 is determined in conjunction with spring 39. The lower half of the system below the nodal line is similar to the upper half of the system with the exception that radiating face or surface 41 of mass 43 operates into a pressure-release material 45. The lower half of the system provides a resonator termination for the upper half. the length of the spring 39 which in turn moves masses 35 and 43 due to the magnetostrictive effect. Thus, the energy is reflected in the lower half of the system because of pressure-release material 45 and in the upper half of the system the energy is transferred to medium 37 at face the fabrication of high-frequency piston-type transducers.

From the foregoing discussion it can be seen that the wagon-wheel type element provides means-for producing a high-frequency acoustic wave having a uniform response pattern in one plane with an uninterrupted a1- Alternating flux in coils 19 induce a change in been shown and describedherein; it is not intended that the invention be limited to' 'such disclosure, but that changes and modifications can be made and incorporated within the scope of the claims. I

What'is claimed:

1. A transducer element comprising a plurality of thin wagon-wheel magnetostrictive laminations, said lamina tions being arranged in a face to-face relationship, insulated from each other, means for consolidating said laminations to form a first cylinder and a second cylinder concentric with such first cylinder radially separated from each other by equally spaced radial spokes, pressurerelease material coextensive with and afiixed to the ring surface of one of such cylinders and cemented to said spokes, and a coil electromagentically coupled to said spokes. H

2. A transducer element comprising a plurality of thin wagon-wheel magnetostrictive laminations, said laminations being arranged in a face-to-face relationship insulated from each other, means for consolidating said laminations to form a first cylinder and a second cylinder concentric with such first cylinderradially separated from each other by equally spaced radial spokes, pressure-re lease material coextensive with and atfixed to the inside ring surface of such first cylinder and cemented to said spokes, and a coil electromagnetically coupled to said spokes.

3. A transducer element comprising a plurality of thin wagon-Wheel magnetostrictive laminations, said laminations being arranged in a face-to-face relationship insulated from each other, means for consolidating said laminations to form a first cylinder and a second cylinder concentric with such firstcylinder radially separated from each other by equally spaced radial spokes, pressurerelease material coextensive with and afiixed to the outside ring surface of such second cylinder and cemented to said spokes, and a coil electromagnetically coupled to said spokes.

4. A compressional-wave translating device comprising a core ofwagon-wheel configuration including two I concentric cylinders and equally spaced radial spokes connecting said cylinders, said cylinders and radial spokes being. of magnetostrictive material, pressure-release material coextensive with and affixed to the inside ring surface of said core and cemented to said radial spokes, a coil magnetically coupled to said core, and means for mounting said core.

5. The invention as described in claim 4 wherein said core consists of a plurality of thin wagomwheel shaped laminations of magnetostrictive material consolidated into a packet, said laminations arranged in a face-to-face relationship insulated from each other.

6. A compressional-wave translating device comprising a core ofwagon-wheel configuration including two concentric cylinders and equally spaced radial spokes connecting saidcylinders, said cylinders and radial spokes being of magnetostrictive material, pressurerelease material coextensive with and affixed to the outside" ring Kallmeyer Feb. 20, 2,434,285 Peek- Jan. 13, 1948 2,638,577 Harris May 12, 1953 FOREIGN PATENTS 607,048 Germany J une 3 

